Great Plains

The Great Plains is a broad expanse of flatland in North America. The region stretches east of the Rocky Mountains, much of it covered in prairie, steppe, and grassland. They are the western part of the Interior Plains, which include the mixed grass prairie, the Tallgrass prairie between the Great Lakes and Appalachian Plateau, and the Taiga Plains and Boreal Plains ecozones in Northern Canada. "Great Plains", or Western Plains, is also the ecoregion of the Great Plains or the western portion of the Great Plains, some of which in the farthest west is known as the High Plains.

The Great Plains lie across both the Central United States and Western Canada, encompassing:

The term "Great Plains" is used in the United States to describe a sub-section of the even more vast Interior Plains physiographic division, which covers much of the interior of North America. It also has currency as a region of human geography, referring to the Plains Indians or the Plains states.^{[citation needed]}

In Canada the term is rarely used; Natural Resources Canada, the government department responsible for official mapping, treats the Interior Plains as one unit consisting of several related plateaus and plains. There is no region referred to as the "Great Plains" in the Atlas of Canada. In terms of human geography, the term "prairie" is more commonly used in Canada, and the region is known as the Canadian Prairies, prairie provinces or simply "the prairies".

The North American Environmental Atlas, produced by the Commission for Environmental Cooperation, a North American Free Trade Agreement (NAFTA) agency composed of the geographical agencies of the Mexican, American, and Canadian governments, uses the "Great Plains" as an ecoregion synonymous with predominant prairies and grasslands rather than as physiographic region defined by topography. The Great Plains ecoregion includes five sub-regions: Temperate Prairies, West-Central Semi-Arid Prairies, South-Central Semi-Arid Prairies, Texas Louisiana Coastal Plains, and Tamaulipas-Texas Semi-Arid Plain, which overlap or expand upon other Great Plains designations.

The region is about 500 mi (800 km) east to west and 2,000 mi (3,200 km) north to south. Much of the region was home to American bison herds until they were hunted to near extinction during the mid/late-19th century. It has an area of approximately 500,000 sq mi (1,300,000 km²). Current thinking regarding the geographic boundaries of the Great Plains is shown by this map at the Center for Great Plains Studies, University of Nebraska–Lincoln. This definition, however, is primarily ecological, not physiographic. The Boreal Plains of Western Canada are physiographically the same, but differentiated by their tundra and forest (rather than grassland) appearance.

The term "Great Plains", for the region west of about the 96th meridian west and east of the Rocky Mountains, was not generally used before the early 20th century. Nevin Fenneman's 1916 study Physiographic Subdivision of the United States brought the term Great Plains into more widespread usage. Before that the region was almost invariably called the High Plains, in contrast to the lower elevation Prairie Plains of the Midwestern states. Today the term "High Plains" is used for a subregion of the Great Plains. The term still remains little-used in Canada compared to the more common "prairie".

The Great Plains are the westernmost portion of the vast North American Interior Plains, which extend east to the Appalachian Plateau. The United States Geological Survey divides the Great Plains in the United States into ten physiographic subdivisions: